Action potential

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What do neurons have on their surface membranes?
sodium-potassium pumps
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What do they pump out?
sodium ions by active transport
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how many sodium ions are moved out?
three
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How many potassium ions are moved in?
2
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What are there in the membrane that allow the passage of sodium?
channels
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What happens at rest?
A few K+ channels are open
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What are potassium ions able to do?
diffuse back out of the cell, down their concentration gradient
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As a result, What does the neurone have?
more positive ions outside than inside
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What is there a potential difference across?
the axon membrane with a charge of about 70mV
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What is this called?
resting potential
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What happens when a receptor receives a stimulus?
It can cause a different set of sodium channels to open
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What does this allow the sodium ons to do?
flood into the cell
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Down the?
electrochemical gradient
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What does this rapidly reverse?
potential difference across the cell membrane
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What does this make it?
less negative inside
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The neurone is what>
Depolarised
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What do the sodium ions continue to do? Until ?
flood the cell until it has become positive inside
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reaching what voltage?
+30mv
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What happens at this voltage?
The sodium ion channels then close
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What does this change in potential difference across the membrane also causes what?
a number of potassium ion channels to open
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What channels are these?
voltage-gated channels
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Why?
they open when the potential difference across the membrane is positive inside
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What can potassium ions now do?
flood out of the axon, down their electrochemical gradient
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What does this make?
the chage inside less positive
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What does this drop to?
down to a little below the value of the resting potential
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AKA?
hyperpolarisation
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What is this time taken for the axon to restore its resting potential called?
refractory period
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Other cards in this set

Card 2

Front

What do they pump out?

Back

sodium ions by active transport

Card 3

Front

how many sodium ions are moved out?

Back

Preview of the front of card 3

Card 4

Front

How many potassium ions are moved in?

Back

Preview of the front of card 4

Card 5

Front

What are there in the membrane that allow the passage of sodium?

Back

Preview of the front of card 5
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